2019 ● 40 ● 9

art. 40 (9) — Published on 18 October 2019www.cryptogamie.com/algologie

Algologiecryptogamie

Snežana B. SIMIĆ, Aleksandra B. MITROVIĆ & Nevena B. ĐORĐEVIĆ

New data on the morphology, reproduction and distribution of a freshwater brown alga

Porterinema fluviatile (Porter) Waern (Phaeophyceae)

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Ecoevolutionary dynamics of algae in a changing worldStacy Krueger-HadfieldDepartment of Biology, University of Alabama, 1300 University Blvd, Birmingham, AL 35294Jana KulicHovaDepartment of Botany, Charles University in Prague, Czech Repubwliccecilia ToTTiDipartimento di Scienze della Vita e dell’Ambiente, Università Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona, Italy.

Phylogenetic systematics, species delimitation & genetics of speciationSylvain faugeronUMI3614 Evolutionary Biology and Ecology of Algae, Departamento de Ecología, Facultad de Ciencias Biologicas, Pontificia Universidad Catolica de Chile, Av. Bernardo O’Higgins 340, Santiago, ChileMarie-laure guilleMinInstituto de Ciencias Ambientales y Evolutivas, Universidad Austral de CHile, Valdivia, Chilediana SarnoDepartment of Integrative Marine Ecology, Stazione Zoologica Anton Dohrn, Villa Comunale, 80121 Napoli, Italy

Comparative evolutionary genomics of algaenicolas BlouinDept of Molecular Biology, University of Wyoming, Dept 3944, 1000 E University Ave, Laramie, WY 82071, USAHeroen verBruggenSchool of BioSciences, University of Melbourne, Victoria, 3010 Australia

Algal physiology & photosynthesisMario giordanoLaboratorio di Fisiologia delle Alghe e delle Piante, Dipartimento di Scienze della Vita e dell’Ambiente, Università Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona, ItalyJanet KüBlerCalifornia State University Northridge, Department of Biology, California State University, Northridge, CA 91330-8303, USA

Prokaryotic algaenico SalMaSoIASMA Research and Innovation Centre, Fondazione Mach-Istituto Agrario di S. Michele all’Adige, Limnology and River Ecology, Via E. Mach, 1 - I-38010, S. Michele all’Adige, Trento, Italyvitor vaSconceloSFaculdade de Ciências da Universidade do Porto and CIIMAR, Rua do Campo Alegre, s/n, 4169-007 Porto, Portugal

couverture / cover: Created from Figure 3B of this article

95CRYPTOGAMIE, ALGOLOGIE • 2019 • 40 (9) © Publications scientifiques du Muséum national d’Histoire naturelle, Paris. www.cryptogamie.com/algologie

New data on the morphology, reproduction and distribution of a freshwater brown alga Porterinema fluviatile (Porter) Waern (Phaeophyceae)

Simić S. B., Mitrović A. B. & Đorđević N. B. 2019.— New data on the morphology, reproduction and distribution of a freshwater brown alga Porterinema fluviatile (Porter) Waern (Phaeophyceae). Crypto gamie, Algologie 40 (9): 95-103. https://doi.org/10.5252/cryptogamie-algologie2019v40a9. http://cryptogamie.com/algologie/40/9

AbstrActThis paper provides information on the morphology, reproduction and distribution of a freshwater brown alga, Porterinema fluviatile (Porter) Waern (Phaeophyceae). The alga was recorded in oligotrophic water from Mlava Spring, a karst limnocrene in eastern Serbia (44°11’298”N, 21°47’021”E). This is the first record of freshwater brown algae in general in Serbia, and the first record of P. fluviatile in southeastern Europe. The thallus of P. fluviatile formed small, dark-brown tufts, with multicellular, uniseriate filaments that were irregularly branched. An anastomosis was noticeable between some filaments. The vegetative cells of the young filaments were cylindrical (17-38 μm long × 2.5-4.0 μm wide). The cells had 1 or 2, rarely 3, plate-like parietal plastids. The reproductive organs of P. fluviatile (asexual reproduction) originate from the transformation of vegetative cells. Elongated vegetative cells develop inflated vegetative cells (5-10 μm in diameter) with lipid droplets. Further transformation of these cells leads to the formation of intercalary plurilocular sporangia with 4 to 8 (rarely 16) cells. Nonmotile, round aplanospores, which develop by protoplast division in elongated vegetative cells, are described for the first time in this species.

Snežana B. SIMIĆ Aleksandra B. MITROVIĆ

aleksandra.mitrovic@pmf.kg.ac.rs (corresponding author)

Nevena B. ĐORĐEVIĆUniversity of Kragujevac, Faculty of Science,

Institute of Biology and Ecology, 34000 Kragujevac (Serbia)

Submitted on 25 September 2018 | Accepted on 9 April 2019 | Published on 18 October 2019

Key wordsFreshwater,

Phaeophyceae,lipid droplets,

plurilocular sporangia,aplanospores.

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Apistonema pyrenigerum, which Dop (1979) regarded to be a synonym for P. fluviatile. Jaasund (1965) collected a marine specimen of Porterinema from the upper sublittoral of Lakes-fjord in northern Norway, naming it a new species, P. marina, separated from P. fluviatile on the basis of its morphological characteristics and marine habitat. Jaasund (1965) established P. marina on the strength of the filaments which were more uniform and did not exhibit variation in size, similar to those of P. fluviatile. As the species was found inside of marine algae Punctaria plantaginea (Roth) Greville and Dictyosiphon chord-aria Areschoug, Jaasund (1965) considered the species to be different from species already identified. Wilce et al. (1970) and Rhodes (1972) regard these species as conspecifics, with P. marina as a synonym of P. fluviatile. Report of the new genus Pseudobodanella Gerloff in Europe (Gerloff 1967), which was done by the holotype species Pseudobodanella peterfii Gerloff, was also regarded as identical to P. fluviatile (Wehr 2015). Even after Waern (1952) had unified several of these taxa, Geitler (1970) collected the alga from Neusiedler Sea and identi-fied it as Apistonema expansum. Subsequently, Dop (1979) and Bourrelly (1981) both suggested the earlier findings of A. pyrenigerum (Belcher 1959), A. expansum (Geitler 1970) and P. marina (Jaasund 1965) to be synonyms of P. fluviatile.

The classification of P. fluviatile is also problematic. When first described, it was classified in the order Ralfsiales (Porter 1894). According to the terminal unilocular sporangia resem-bling those of Lithoderma and Sorapion, Waern (1952) classified it in the family Lithodermataceae. Tanaka & Chihara (1981) suggested that P. fluviatile does not belong to Lithodermatace or Ralfsiales on the basis of its unique plurilocular sporangia, thalli composed only from creeping filaments attached to the substratum, and the lack of clearly erect filaments. Accord-ing to a recent molecular analysis (Kusel-Fetzmann & Schagerl 1992; McCauley & Wehr 2007) P. fluviatile is considered to be “insertae sedis” in the class Phaeophyceae.

résuméNouvelles données sur la morphologie, la reproduction et la distribution d’une algue brune d’eau douce Porterinema fluviatile (Porter) Waern (Phaeophyceae).Cet article fournit des informations sur la morphologie, la reproduction et la distribution d’une algue brune d’eau douce, Porterinema fluviatile (Porter) Waern (Phaeophyceae). L’algue a été observée dans les eaux oligotrophes de la source Mlava, une source limnocrène karstique de Serbie orientale (44°11’298”N, 21°47’021”E). Il s’agit du premier signalement d’algues brunes d’eau douce en général en Serbie et du premier signalement de P. fluviatile en Europe du Sud-Est. Porterinema fluviatile forme de petites touffes brun foncé, avec des filaments multicellulaires, unisériés, à ramifications irrégulières. Une anastomose est perceptible entre certains filaments. Les cellules végétatives des jeunes filaments sont cylindriques (17-38 μm de long × 2,5-4,0 μm de large). Les cellules présentent 1 ou 2, rarement 3, plastes pariétaux en forme de plaquettes. Les organes reproducteurs de P. fluviatile (reproduction asexuée) proviennent de la transformation de cellules végétatives. Les cellules végétatives allongées développent des cellules végétatives gonflées (5-10 μm de diamètre) avec des gouttelettes lipidiques. La transformation ultérieure de ces cellules entraîne la formation de sporanges pluriloculaires inter-calaires de 4 à 8 (rarement 16) cellules. Des aplanospores rondes non mobiles, qui se développent par division protoplastique dans des cellules végétatives allongées, sont décrites pour la première fois chez cette espèce.

INTRODUCTION

Brown algae (Phaeophyceae) are characterized by a large diversity of their species, which are almost exclusively marine organisms. Only seven species, currently classified in six genera, occur in freshwater habitats: Bodanella lauterborni W.M.Zimmermann, Ectocarpus siliculosus (Dillwyn) Lyngbye, Heribaudiella fluviatilis (Areschoug) Svedelius, Pleurocladia lacustris A.Braun, Porterinema fluviatile (Porter) Waern, Sphacelaria fluviatilis C.-C.Jao and S. lacustris Schloesser & Blum (van den Hoek et al. 1995; Eloranta et al. 2011; Wehr 2016). Other than in freshwaters, E. siliculosus, P. lacustris and P. fluviatile may colonize brackish and marine habitats (Waern 1952; Jaasund 1965; Wehr 2015).

According to the available literature, P. fluviatile has been recorded in marine waters, estuaries, and several putative fresh-water habitats (Wehr 2015). The species is distributed across a small number of locations in Europe (Austria: Geitler 1970; Kusel-Fetzmann 2014; England: Belcher 1959; Germany: Porter 1894; McCauley & Wehr 2007; Sweden: Waern 1952; Norway: Jaasund 1965; Netherlands: Dop & Vroman 1976; Dop 1979) and North America (Wilce et al. 1970; Rhodes 1972). The majority of these records are from brackish-water habitats (Wilce et al. 1970, Wehr 2016).

Porterinema fluviatile is the only member of the monotypic genus Porterinema (Eloranta et al. 2011), which is taxonomi-cally enigmatic, as it has been insufficiently explored and has several synonymies, making this a problematic genus (Wehr 2015). The species was described originally as Streblonema fluviatile (Porter 1894). In 1946 Waern collected a very simi-lar alga from coastal waters in the Öregrund archipelago and identified it as Porterinema fluviatile (Waern 1952). Waern compared his finding with Porter’s description and concluded that these two specimens were the same species (Waern 1952). Belcher (1959) also collected a similar alga, identified as

mots clésEaux douces,dulcaquicole,Phéophycées,

goutellettes lipidiques,sporanges pluriloculaires,

aplanospores.

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Because of the limited and occasionally contradictory information on this species, the goal of this study was to provide new information on the morphology, reproduction and distribution of P. fluviatile, based on a newly-discovered population from a freshwater karst spring in eastern Serbia.

MATERIAL AND METHODS

Algal material was collected in karst limnocrene Mlava Spring, located in eastern Serbia (44°11’298”N, 21°47’021”E), southeastern Europe (Fig. 1), at an altitude of 314 m. This spring receives water from the karst aquifer of the calcareous massif of the Beljanica Mountains, with a diluted system of underground canals. Water reaches the surface through an inlet siphonal channel from a depth of more than 80 m (Kojadinović 2013).

This research was carried out in October 2014, August and October 2015 and in October 2016, 2017 and 2018. The samples of water were collected from a siphonal channel at

a depth of 5, 10 and 20 m (Ruttner bottle, 2 L), a spring lake (plankton net, macrophytes) and part of the brook near the spring (scraping from rocks, pipette along the sand surface, tear off the thalli from the substrate with tweezers, macrophytes). The samples were fixed with 4% formaldehyde solution and they are stored at the Institute of Biology and Ecology, Faculty of Science, University of Kragujevac, Serbia.

The morphological characteristics of the algal material were analyzed under a Motic BA310 microscope with a magnification of up to 800-1000× and photographed with a Bresser (9MP) and MicroCamLab. The macroalgal tufts were identified according to Eloranta et al. (2011) and Wehr (2015) while the diatom and cyanobacterial samples were identified accord-ing to Krammer & Lange-Bertalot (1991a, b) and Komárek & Anagnostidis (2005), respectively.

The physical and chemical parameters of the water were measured in the field according to the American Public Health Association (1995), while the bicarbonate and carbonate con-centrations (mg L-1) were measured at the Institute of Public Health in Kragujevac.

fiG. 1. — Study area map. Location of the karst limnocrene Mlava Spring and cross section through the siphonal channel.

SERBIA

CROATIA

HUNGARY

ROMANIA

MONTENEGRO

ALBANIAMACEDONIA

BULGARIA

Mlava Spring

BOSNIA AND HERZEGOVINA

0 m

–20 m

–40 m

–60 m

–80 m

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RESULTS

Morphology and reproduction of speciMens

The macroscopic thalli of P. fluviatile were dark-brown, up to 3 mm in size, composed of loosely arranged, irregularly branched filaments (Table 1). The filaments were composed of elongate vegetative cells (17-38 μm long × 2.5-4.0 μm wide) (Fig. 2A; Table 1). An anastomosis was noticeable between some filaments (Fig. 2A; Table 1). The vegetative cells had 1-2 (rarely 3) plate-like parietal chromatophores (Fig. 2B; Table 1).

The vegetative cells transform into reproductive organs by shortening and spreading the elongated vegetative cells (Fig. 2C, D). The cell wall later thickens, while within the cells there is an accumulation of cellular content and gradual formation of a transverse partition (12-25 μm long × 4.0-7.5 μm wide; 2.5-4.5 μm wide in narrow sections) (Fig. 2D). From this, two new inflated (oval-shaped) veg-etative cells (5-10 μm in diameter) with a large number of lipid droplets (Fig. 3A, B; Table 1) develop from the original elongated vegetative cell. Further transformation of these newly formed, inflated vegetative cells leads to the forma-tion of dark, roughly oval cells with thick walls (5.5-8.0 μm long × 5.0-7.5 μm wide) (Fig. 3A, B). The intercalary pluri-locular sporangia (12.5-39.0 μm long × 10-17 μμm wide) (Fig. 3C, D) develop by means of the division of these cells. The plurilocular sporangia may be constructed from

4-8 (rarely 16) cells (Table 1). Cells inside the plurilocular sporangia are usually 5-10 μm in diameter (Fig. 3E). The plurilocular sporangia may be sessile (Table 1) or on unicel-lular pedicels (Fig. 3E; Table 1).

The axial cells of the filaments are elongated, gradually narrowing to the top (Fig. 3A, B; Table 1). In most cells comprising the apical filaments, the protoplast is divided into two to seven sections (Table 1). On each of these sections, a cell wall is formed while they are developing in a vegeta-tive cell (Fig. 4A, B). This is how nonmotile aplanospores (Fig. 4C) are formed. Aplanospores are round, 2-3 μm in diameter while they are contained within a vegetative cell; they are released by rupturing of the cell wall. The diameter of the released aplanospores is 2.5-3.5 μm (Fig. 4C). Mature aplanospores, from which the new thallus develops, are 5.0-6.5 μm in diameter (Fig. 4D; Table 1).

distribution and ecology

Porterinema fluviatile was found in a submerged siphonal channel of the freshwater Mlava Spring at a depth of 20 m in October 2014. However, during a research conducted in August and October 2015 and October 2016, 2017 and 2018 thalli of P. fluviatile was not found. The physical and chemical parameters of water are presented in Table 2. In the sample of collected water, diatom species Cyclotella ocellata Pantocsek, Gomphonema sp., Melosira varians C.Agardh, and Nitzschia dissipata (Kützing) Raben-

table 1. — Comparative review of the morphological and reproductive features of Porterinema fluviatile (Porter) Waern.

Characteristics of species Sample from Mlava Spring (Serbia) Eloranta et al. 2011 Wehr 2015

Thalli Brown and dark in colour; loosely arranged, irregularly branched filaments; anastomoses are noticeable; axial cells of filaments are elongated, gradually narrowing to the top

Creeping thalli form loose discs of radiating branched filaments; short erect filaments

Thalli are monostromatic, brown disc-shaped plates or loosely arranged, spreading filaments; creeping, irregularly branched uniseriate filaments, with short erect filaments, produced infrequently

Cellular hairs not present Multicellular, with basal growth; 3-8 µm wide, up to 200 µm long and sheathed at the base

Multicellular; 3-8 μm wide, 100-200 μm long; may be sheathed at their base

Cylindrical vegetative cells

2.5-4.0 µm width17-38 µm length

no data no data

Inflated vegetative cells

5-10 µm in diameter 6-8 µm in diameter 6-12 μm in diameter

Plastids 1-2 (rarely 3) plate-like, parietal 2 (occasionally 3) plate-like 1 to 3 lobed, golden-brown, parietal chloroplasts

Pyrenoids not observed only visible using a transmission electron microscope

pyrenoids obscure; visible via electron microscopy

Sporangia Intercalary plurilocular sporangia; 4-8 (rarely 16) cells per sporangia; sessile or on unicellular pedicels; unilocular sporangia were not observed

Pear-shaped unilocular sporangia; plurilocular sporangia intercalary, sessile, on one or two pedicels, or terminal

Plurilocular sporangia, intercalary (occasionally terminal); occasionally in four-celled clusters or “crowns” on pedicels or sessile; sometimes produced in clusters of up to 32 sporangia; unilocular sporangia were rare

Zoospores not observed present presentAplanospores Develops by protoplast division of

elongated vegetative cells; 2-7 round aplanospores per cell; mature aplanospores 5.0-6.5 µm in diameter

not observed not observed

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horst were also recorded. The cyanobacterial species Romeria leopoliensis (Raciborski) Koczwara (Fig. 5) develops as an epiphyte on some parts of the P. fluviatile thalli.

DISCUSSION

Data on the morphology, reproduction, ecology and dis-tribution of P. fluviatile are very scarce and incomplete because there have only been a small number of collections (Wehr 2016).

The thalli of P. fluviatile collected from the Mlava Spring were composed of loosely arranged, irregularly branched filaments. An anastomosis was noticeable between some of the filaments (Table 1). Cellular hairs described by Eloranta et al. (2011) and Wehr (2015) (Table 1) were not recorded in the present material, but the axial cells of the filaments were elongated, gradually narrowing to the top (Fig. 3A, B; Table 1). Previous studies did not record the shape or dimen-sions of the young vegetative cells, but only the larger, inflated vegetative cells (Porter 1894; Waern 1952; Rau-tenberg 1960; Jaasund 1965; Reith 1969; Geitler 1970; Wilce et al. 1970; Dop 1979, Eloranta et al. 2011; Wehr 2015). Previous studies describe the number of plastids as

1 to 2 per cell (rarely 3), which are plate-like or lobed, also described by (Eloranta et al. 2011; Wehr 2015) (Table 1). No pyrenoids were noticed in our material. According to Eloranta et al. (2011) and Wehr (2015), pyrenoids are vis-ible only via an electronic microscope (Table 1). The same authors described inflated vegetative cells 6-8 μm or 6-12 μm in diameter. In our material, the inflated cells were more or less oval, but similar in size, 5-12 μm in diameter (Table 1).

According to available data, the reproduction of P. flu-viatile is asexual, with biflagellate zoospores produced in plurilocular, rarely unilocular, sporangia. It is suggested that critical identification of P. fluviatile is based on its unique four-celled (crown-shaped) sporangia (Porter 1894; Waern 1952; Rautenberg 1960; Jaasund 1965; Reith 1969; Geitler 1970; Wilce et al. 1970; Dop 1979). In material from Mlava Spring, only intercalary plurilocular sporangia were observed, which were composed of 4-8 (rarely 16) cells. More than four cells in the plurilocular sporangia were also observed by Dop (1979) and Kusel-Fetzmann (2014). Dop (1979) suggested that there are two types of quite different pluri-locular sporangia: the intercalary type, which develops by the partition of cells whose cell wall eventually surrounds the whole sporangia, and the crown-shaped terminal type that occurs as a result of cleavage of the cells, whereby four

fiG. 2. — A, Young filaments composed from elongated vegetative cells with an anastomosis () between their filaments. Filament with elongated vegetative cells in the transformation process (); B, young filaments composed from elongated vegetative cells with plastids; C, D, first phase of the transformation of elongated vegetative cells to inflated vegetative cells. Scale bars: 10 µm.

D

B

C

A

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loosely connected spores occur on a common pedicel. In the material from the Mlava Spring, no crown-shaped ter-minal plurilocular sporangia were observed, while intercalary sporangia were abundant (Table 1). Dop (1979) suggested that elevated chloride concentration affects the growth, thalli structure and production of sporangia, but not their formation. According to Wehr (2016) plurilocular sporan-gia develop in a large number while unilocular sporangia are rare. In our material, unilocular sporangia, as well as zoospores, were not observed (Table 1).

In the material from the Mlava Spring, we recorded the divi-sion of the protoplast into several parts and the forming of immobile unicellular aplanospores in the axial cells of the fila-ments. The number of aplanospores is two to seven per cell (Table 1). The reproduction of P. fluviatile with nonmotile

aplanospores has not yet been described. In the filamentous brown alga Sphacelaria, asexual propagation without flagel-lated spores may occur, and a new thallus can develop from multicellular triradiate propagules after they are released from the thallus (Eloranta et al. 2011).

Data on the geographical distribution and ecology of P. flu-viatile are very scarce. This species has been collected from approximately 14 localities in Europe and North America, usually in brackish waters, and rarely from marine or fresh-water habitats (Wehr 2015). Our collection of P. fluviatile represents the first occurrence of this species in Serbia, as well as the first record in southeastern Europe. It has been observed that P. fluviatile occurs in channels (Rhodes 1972), streams (Gerloff 1967), diches (Dop & Vroman 1976; McCauley & Wehr 2007), ponds (Dop & Vroman 1976),

fiG. 3. — A, B, Newly formed inflated vegetative cells (ic) with thick walls and a large number of lipid droplets (ld), formation of the approximately oval dark cells (dc) with thick walls, elongated axial cells (eac) of filaments, gradually narrowing to the top; C, D, developing intercalary plurilocular sporangia; E, intercalary plurilocular sporangia on the pedicels. Scale bars: 10 µm.

A

B

C

D

E

eac

eacdc

ldic

eaceac

dc

ld ic

ld

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gravel pits (Belcher 1959), marshes (Wilce et al. 1970; Rhodes 1972), lakes (Gerloff 1967; Geitler 1970; Kusel-Fetzmann 2014), fjords (Jaasund 1965), estuaries (Porter 1894; Wilce et al. 1970) and marine habitats (Waern 1952). According to Porter (1894), Waern (1952), Belcher (1959), Jaasund (1965), Gerloff (1967), Geitler (1970), Wilce et al. (1970), Rhodes (1972), Dop & Vroman (1976), Dop (1979) and Kusel-Fetzmann (2014) P. fluviatile is a benthic alga which develops as epiphytic, endophytic, epilithic or epizoic. Finding

fiG. 4. — A, B, Protoplast division into several parts in apical filament cells resulting in the formation of aplanospores; C, nonmotile aplanospores; D, new thalli developing from aplanospores. Scale bars: 10 µm.

A B

C D

the P. fluviatile in a plankton sample is unusual. As the spe-cies is considered to be a benthic alga, we suppose that it was cut off from the rocky substrate of the siphonous chan-nel walls. Another theory is that it was brought by ground water from another habitat, which presumably ties in with the fact that we did not find it in our later research and that we found a very small amount of the material.

Based on the first finding of P. fluviatile by Waern in 1952, the species was considered an exclusively brackish

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species, which was a logical assumption at that time. Sub-sequent findings in freshwater and marine habitats indicate that P. fluviatile is extremely tolerant to salinity, since it was found in different salinity conditions (0 to 35.5 ‰ in natural habitats) (Eloranta et al. 2011; Wehr 2016). The karst limnocrene Mlava Spring is clearly non-saline, which compared to previous data supports the fact that P. fluvia-tile has a wide ecological valence in regard to salinity (Dop 1979). Freshwater members of the Phaeophyceae class tend to occur in neutral to slightly alkaline systems and span oligotrophic to eutrophic waters, but they are not tolerant to organic pollution (Eloranta et al. 2011). In our investiga-tion, the species was found in oligotrophic, slightly alkaline and well aerated water, rich with soluble ionizing substances (Table 2). According to Kusel-Fetzmann (2014) P. fluviatile inhabits eutrophic water.

CONCLUSION

This study represents a significant contribution to the knowl-edge of the morphology and especially the reproduction of P. fluviatile. The asexual reproduction and transformation of vegetative cells into plurilocular sporangia is described in detail. Also, asexual reproduction with nonmotile aplanospores is described for the first time for this species. Subsequent molecular analysis of the material could contribute to the clearer phylogenetic position of this species. Our record is the first record of freshwater brown algae in general in Serbia, and accordingly the first record of P. fluviatile in southeastern Europe.

AcknowledgementsThis work was supported by the Ministry of Education and Science and Technological Development of the Republic of Serbia (Project No. TR 31011, III 43002). We want to thank Prof. John Wehr (Fordham University, New York; Department of Biological Sciences) for his suggestions and guidelines that were very useful during this research. We would also like to thank the reviewers for their comments and constructive and helpful suggestions.

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table 2. — The physical and chemical parameters of water from the Mlava Spring in October 2014 at a depth of 20 m.

Parameter Mlava Spring (20 m depth)Temperature (°C) 11.30Conductivity (μS cm–1) 400рН 8.39Dissolved oxygen (mg L–1) 9.64Oxygen saturation (%) 91.7Nitrate (mg N L–1) < 0.02Nitrite (mg N L–1) < 0.01Ammonium (mg N L–1) < 0.02Phosphate (mg P L–1) 0.19Secchi depth (transparency, m) 3Bicarbonate (HCO3) (mg L–1) 234.8Carbonate (CO3) (mg L–1) 0

103

New data on a freshwater brown alga Porterinema fluviatile

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Submitted on 25 September 2018 accepted on 9 April 2019;

published on 18 October 2019.